1. Technical Field
The invention relates to the art of dewatering and drying of polymers and elastomers. More particularly, the invention relates to the art of mechanical dewatering and drying machines that are used in the finishing of the formulation of certain polymers and elastomers. Still more particularly, the invention is directed to an improved dewatering and drying machine and accompanying process which reduce the escape of fine particles encountered in prior art dewatering and drying machines and processes, employs fewer machines than prior art dewatering and drying processes, and reduces the volatility of the dewatering process.
2. Background Art
In the formulation or production of certain polymers and synthetic elastomers, a wet slurry of particles is often created. The slurry typically consists of water and the formulated polymer or elastomer in crumb form, along with fine particles, which are known in the art as fines. These fines are typically in a size range of from about 0.1 millimeters (mm) in diameter to about 4.0 mm in diameter. In order for the polymer or elastomer to be prepared for further use, the slurry water must be removed and the moisture level of the polymer or elastomer then reduced to a level of about 0.5 percent (%) water by weight. The reduction of moisture is often performed by a dewatering and drying process, which will be described in detail below.
In the art, dewatering is often viewed as a first step in which the moisture of the polymer or elastomer is reduced to a level of about 5% to about 15% of water by weight, and drying is viewed as a second step in which the moisture of the polymer or elastomer is reduced from the 5-15% percent level to a level of about 0.5% water by weight. However, for the purpose of convenience, reference below shall be made to the term dewatering with the understanding that such reference also includes drying, without affecting the overall concept or operation of the invention.
In the prior art, during the dewatering process, many fines typically escape with the moisture that is being removed, and must either then be recycled using undesirable additional equipment and steps, or disposed of, which creates undesirable waste. In addition, prior art dewatering processes typically employ more than one dewatering machine, each of which involves a cost investment to purchase, operate and maintain. Moreover, the dewatering process often involves the escape of vapors and/or particles that may be volatile, and must be contained. However, the design of certain prior art dewatering machines makes such containment difficult.
As a result, there is a need in the art for an improved dewatering machine and accompanying process that overcome the disadvantages of the prior art by providing removal of sufficient water with a single machine, reduction of the escape of fines, and reduction of volatility. The improved dewatering machine and process of the present invention satisfies this need, as will be described in detail below.